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Study reaffirms inflammation in neurocircuitry of OCD

Recent findings indicated elevated translocator protein distribution volume in the dorsal caudate, orbitofrontal cortex, thalamus, ventral striatum, dorsal putamen and anterior cingulate cortex in obsessive compulsive disorder.

“For a small percentage of obsessive-compulsive disorder (OCD) cases exhibiting additional neuropsychiatric symptoms, it was proposed that neuroinflammation occurs in the basal ganglia as an autoimmune response to infections. However, it is possible that elevated neuroinflammation, inducible by a diverse range of mechanisms, is important throughout the cortico-striato-thalamo-cortical circuit of OCD,” Sophia Attwells, HBSc, of Centre for Addiction and Mental Health, Toronto, and colleagues wrote.

To determine if translocator protein distribution volume (TSPO V_T) is higher in the dorsal caudate, orbitofrontal cortex, thalamus, ventral striatum, dorsal putamen and anterior cingulate cortex in OCD, researchers conducted a case-control study among 20 individuals with OCD and 20 age-matched healthy controls. Study participants underwent a fluorine F 18-labeled N-(2(2-fluoroethoxy)benzyl)-N-(4-phenoxypyridin-3-yl)acetamide PET scan. Participants with OCD had a mean age of 27.4 years.

Participants with OCD had significantly higher TSPO V_T in all studied brain regions (P = .03).

There were robust differences in individual regions, including elevations in the dorsal caudate (35.6%; P < .001), orbitofrontal cortex (30.9%; P = .001), thalamus (33.5%; P = .001), ventral striatum (33.8%; P = .001), dorsal putamen (32.6%; P = .001), and anterior cingulate cortex (23.5%; P = .004).

Elevated TSPO V_T in the orbitofrontal cortex was significantly associated with greater distress related to preventing compulsive behaviors as reported on the Yale-Brown Obsessive Compulsive Scale (P = .005).

Reanalysis of data excluding two participants with a history of major depressive episode indicated similar results.

“To our knowledge, this study is the strongest evidence to date for inflammation in the brain in OCD. The demonstration of elevated TSPO V_T in the [cortico-striato-thalamo-cortical] circuit addresses a critical gap in the autoimmune/neuroinflammatory theory of OCD,” the researchers wrote. “The regional distribution of greater TSPO V_T throughout the [cortico-striato-thalamo-cortical] circuit argues for consideration of autoimmune mechanisms beyond the basal ganglia and suggests a new opportunity for repurposing immunomodulatory therapies to treat OCD.” – by Amanda Oldt

Disclosure: Atwells reports no relevant financial disclosures. Please see the study for a full list of relevant financial disclosures.